As for me, I think the most overvalued coin today is Ethereum. I don't understand why does it cost so much. It is not decentralized. It is not limited, so there is no deficit. Nowadays it doesn't look innovative. It is not even great as a cryptocurrency. Of course it is great for ICOs, but most of the ICOs are crap. 
Most of this coins will die in future. So it's just a hype and nothing more.
Well, eth WAS very innovative and cool some time ago and now it sort of lives from the recognition of what it did in the past. If we talk like this then bitcoin is the most overvalued coin, since it transactions are taking the hell lot of time as well as are very expensive. Yet it lives and will live, because it was the first one and everyone appreciates it. Most of this coins will die in future. So it's just a hype and nothing more. A lot of people say ripple is overvalued. I don't know, but I think it will rise more anyway.
My #1 choice is Bitcoin cash which is basically another bitcoin, which only has increased block size. I don't think it's really worth all that money.